Also, bummer that it's written in Java. I know that was for easy pluggability into Hadoop, but it makes it tough to write bindings for other languages.
It appears to just be a thin wrapper around HDFS, so the namenode and what not probably applies here.
I take it, the resulting DFS can't be mounted, am I right? If yes, that's a pity. By the way, are there DFS with similar properties (very fast, aggressive memory use) that can be mounted?
I think the NameNode SPOF issue in HDFS is also being dealt with:
"Prior to Hadoop 2.0.0, the NameNode was a single point of failure (SPOF) in an HDFS cluster.
[...] The HDFS High Availability feature addresses the above problems by providing the option of running two redundant NameNodes [...]"